Millemiglia

From this thread https://rennlist.com/forums/964-forum/230022-how-do-i-temporarilly-disable-the-pdas-system.html I now know how to disable PDAS and ABS.

In my quest to minimise understeer while tracking the car I've been doing some reading and I'm not totally happy with disabling the ABS together with PDAS. Therefor I would like to know if it's possible to only disable the lateral differential lock. Since the longitudinal differential lock does help me accelerate out of corners and the ABS saves my tires when breaking hard I really don't want to disable those systems.
There should be some way to prevent the lateral differential lock to actuate.

Adrian

Peter,
If you attempt to disable the lock actuation system, the whole system will fail and switch off resulting in the same impact as disconnecting the connector in the first place.
The longitudinal lock ONLY functions if both rear wheels spin up whilst accelerating.
Ciao,
Adrian.

Millemiglia

Ok, Adrian.
Thanks for the reply.

Red rooster

Out of curiosity, I guess you have the diff lock light flashing away ?
Geoff

garrett376

Peter - I think your search for better handling will be better satisfied by doing things to the suspension, not changing the attitude of the drivetrain. Once your tires get hot, and you nail the throttle out of a tight corner, you will know what I mean when you watch your RPM's go up but not your speed (you're spinning the tire with no traction)!

To affect the attitude all the time, you ought to get a big rear sway bar (22mm adjustable, for example) and put it on max hard setting and I think you'll be happier than wasting that sweet 3.6 torque! Or, as I mentioned before, you simply change your driving style to load the car differently at turn-in (on the brakes at turn in will permit an oversteer situation by loading front tires more). I used to vintage race a 65 911 that was an oversteering nightmare! When I started racing the C4, it eventually occurred to me that different cars need to be driven in different ways: 65 911 was full throttle from the turn-in point through the apex; C4 is on brakes through the turn-in point up to the apex, in most cases.

Not sure if that helps in your search for better C4 handling...

Patrick L

One stupid question: is it possible to install a C2 ABS controller to keep ABS but no PDAS? Just curious.

Adrian

Yes you can do anything. The question is: Is it cost effective? The answer is no. The R&D required, the cost of parts, the labour would make it very expensive with no real guarantee on it working. The cost of just one of those control unit connectors will make you cry. The ABS is 35-pin and the PDAS 55-pin.
Please remember that the 964 C4 first hit the showroom floors in 1989. These questions being asked, are on their 1000th time around.
If it could have been done effectively, believe me it would have been done by now and I would have it installed
I had a recognised Porsche electronic boffin look at it and he gave up, calling it "Bridge too far".
Ciao,
Adrian.

Sten

At your own risk - you can disconnect the wiring to the lock solenoids, and connect a 4 ohm 100 watt resistor across the terminals. Use an aluminium finned resistor(s), and mount it on a piece of sheet aluminium to help dissipate the heat. This will mimic the resistance (but not the inductance) of the coils, and the PDAS control unit will keep it's toys in the cot - i.e. your ABS will still function, and you won't get any warning lights. However, it would probably invalidate your road insurance, so track use only please.
Barry

Millemiglia

Thanks Sten!
I think this is solution I've been looking for, I'll let my workshop look into it.



...as for invalidate my insurance, well, even attending the well organised trackdays of Porsche Club Sweden invalidates your insurance at some insurance companies...